Semiconductor devices are extensively used as memory devices in devices ranging from microcontrollers to credit cards. Semiconductor memory devices may be classified as volatile memory devices, such as DRAMs or SRAMs, which are capable of inputting and outputting data rapidly, but in which the data can be erased with time, and nonvolatile memory devices, such as ROMs, in which inputting and outputting of data are performed slowly, but the data can be stored more permanently. Recently, nonvolatile memories, such as EEPROMs and flash memory devices, in which inputting and outputting of data can be performed electrically, have been developed.
For example, an EEPROM or a flash memory device has a structure in which a tunnel oxide film, a floating electrode, a gate insulating layer, and a control gate electrode are formed on a semiconductor substrate. In an EEPROM or the flash memory device, data can be electrically programmed and erased using a F-N tunneling process and/or a channel hot electron injection process. During the programming and/or the erasing of the data, electrons and/or holes move through the tunnel oxide film between the floating electrode and the semiconductor substrate.
However, in a silicon oxide film that is typically used as the tunnel oxide film, a portion of Si in the oxide film may not be properly bonded to Si or O atoms, resulting in Si dangling bonds and/or imperfect Si bonding states. The presence of dangling Si bonds may impair leakage current properties of the tunnel oxide film and/or electron retention properties of the floating electrode.